Horizontal blind systems typically have an upper channel made of metal and configured to support movement and bearing components for horizontal blind operation. The two main operations are the elevation of the bottom horizontal which automatically collects the suspended horizontal step connectors above it and clears the window opening, and the angular movement of the slats utilized to allow light into the room at high or low angle or to close the louvers completely.
Where the louvers are left horizontal, very little direct light enters through the window unless the sun or exterior lighting is at low angles. Most louvered blinds are constructed so that the louvered width is sufficient for a small overlap to enable the louvers to be closed in either direction from horizontal to shut out the light. Even assuming no bare overlap, the louvers assume a position at horizontal such that the light source is typically lower than a 45° angle before light is admitted. Given a slight overlap, this angle is typically lower, at about 40° to about 43°.
In the summer, it is desired to open the louvers to a horizontal position to admit cooling breezes. However, this action also provides shade from high angle sun light, even if it is desired to admit the sunlight into the room. This action has the advantage in that the blocking of the breezes are minimized, but light can be admitted only by angling the louvers.
In angling the louvers to let in the sunlight (while still providing some privacy), the user must make the louvers track the angle of the sun. When the angle of the sun is tracked, the louvers are angled to enable sunlight to come in sufficiently, but only if the louvers are sufficiently tracking. The angling of the louvers significantly impedes the breeze and air flow into and out of the window opening.
What is needed is a system which will enable alternate ones of the louvers to move close to each other to provide wider gaps in a horizontal blind set. The movement should ideally be able to occur regardless of whether the slats or louvers are horizontal, or non tilted, as well as when the slats or louvers are tilted. The need to facilitate ease of movement is especially important when tilted as light may be admitted to the room while still providing a partial visual barrier to viewing the inside of the room from outside.
In one reference to Lai, U.S. Pat. No. 6,648,048, a complex arrangement is had using a series of adjacent ladders with each ladder having the number of 1/r where r is the number of ladder rungs. Each adjacent ladder can be raised independently with respect to the other ladders. Raising one adjacent ladder moves 1/r slats upward to the adjacent slat. Raising a second ladder moves another 1/r slats up forming an “r” sized bundle.
However, the expense of providing more than a single ladder is tremendous, particularly where that ladder has to be raisable, even over a slight vertical distance. The problems with multiple ladders involve the fact that each additional ladder can move only a limited amount. Most horizontal blind sets don't make accommodation for raising a ladder at all. A cord which is typically attached to the bottom louver collects all of the louvers where the blind set is to be raised. The ladder on a horizontal blind set is typically only for setting the louver angle.
In Lai, the raising of the second ladder involved lifting two sets of cords per side, regardless of whether or not the cords were joined along the way along the path to the user. Further, some mechanism had to be provided to prevent the user from continuing to lift the ladders which could cause the web strings joining the vertical ladder extents to tear or bind against the head rail. In addition to the complicated second ladder, Lai also uses bendable clips to engage the second ladder to enable the user to select which louvers to lift, which causes the areas near the ladders to become crowded into a mess. The device of Lai is complicated and causes extra wear and bunching and inhibits the ability for the user to lift the slat bundle to a height which would otherwise be available without the additional space occupied by the clips and additional ladders.
What is needed is a system which will enable differential lift of horizontal slats in a horizontal blind system to enable one or more slats to be grouped in order to continue to admit some light over a greater range of sun angles while the slats are horizontal, and to admit some breeze flow through while the slates are tilted.